Focal length calculator

This calculator can be used to determine the focal length of a lens using the lens equation.

Input Parameters

Calculation Results

Calculation Formula

1/f = 1/do + 1/di

Where:
f = Focal length
do = Object distance
di = Image distance

Focal length calculator Calculator Usage Guide

Learn how to use the Focal length calculator and its working principles

How to use the calculator

  1. Enter the object distance (do) in centimeters - this is the distance from the object to the lens.
  2. Enter the image distance (di) in centimeters - this is the distance from the lens to the image formed.
  3. Click the "Calculate" button to compute the focal length.
  4. The focal length will be displayed in centimeters.

Working principle

This calculator uses the lens equation to calculate the focal length:

1/f = 1/do + 1/di

Where:

  • f = Focal length of the lens
  • do = Object distance from the lens
  • di = Image distance from the lens

This equation is derived from the principles of geometric optics and applies to both convex (converging) and concave (diverging) lenses.

Applications

This calculator can be used in various fields including:

  • Photography for understanding lens specifications
  • Optics and physics education
  • Designing optical systems
  • Calculating image formation in cameras, microscopes, and telescopes